The present invention relates to a tool for coldforming and drawing operations.
In the description of the background of the present invention that follows reference is made to certain structures and methods, however, such references should not necessarily be construed as an admission that these structures and methods qualify as prior art under the applicable statutory provisions. Applicants reserve the right to demonstrate that any of the referenced subject matter does not constitute prior art with regard to the present invention.
Cemented carbide products are used in tools for different coldforming or drawing operations of materials like; steels, copper alloys, composite materials, etc. Examples of such tools are wire drawing dies, which consist of a cemented carbide nib shrink fit into a metallic holder. Such tools should have a hard and wear resistant body which also should have the following additional properties:
good thermal conductivity
low coefficient of friction (i.e. it may be self-lubricating or assist lubrication with a coolant)
good corrosion resistance
resistance to micro cracking and
high hardness.
When using cemented carbides in tools for the drawing of e.g., steel or other metallic alloys, chemical reactions might occur between the binder metal of the cemented carbide and the metallic alloy. In order to minimize the effects of chemical wear of the binder phase and to improve the wear resistance, a cobalt (binder) content of about 3% and a WC grain size  less than 1 xcexcm is used in hard metals for such applications. Often a low carbon content close to eta phase formation is chosen. In order to maintain the fine grain size, grain growth inhibitors are used such as VC, Cr3C2, etc.
U.S. Pat. No. 5,948,523 discloses coldforming tool with an improved hard wearing surface zone. This has been achieved by a post-sintering heat treatment in a boron nitride containing environment of a hard metal of a suitable composition. The effect is most pronounced when the heat treatment is made of a hard metal which has previously been sintered to achieve a high carbon content through a suitable choice of chemical composition and processing conditions.
It is an object of the present invention to provide a tool for coldforming and drawing operations with a further improved combination of high wear resistance, thermal conductivity, corrosion resistance keeping a good toughness.